Nah, they’re all slightly the wrong size; plus, I’d like something I could use for more than ten minutes without it sawing my nose off. There’s loads for up to 6" devices, but no 7" ones. I’m gonna have to Blue Peter one myself, aren’t I?

Yep. There seem to be a variety of products like this suddenly, adding various bells and whistles beyond what Cardboard has (or not) so you can get a stereoscopic experience from your phone. Which seems like it wouldn’t be good enough to bother with, especially when you’re looking at a cost of one to three hundred dollars, not even counting the phone.